Three-port waveguide switch for selectively connecting one port to either of two other ports



1 12 ECTIVELY CONNECTING TWO OTHER PORTS FROM TEST SOURCE 3 mm WW mm mwmm v n w WT 4 m mm i "M 7 V O A A: I I m .v 0 3/4, 3% 00 %m 4 q w i 2 1 r! 7 H 3 5 I. M H.. v m 9 0 N HENRY M. KINTZEL JUDD BLASQ ATra/u z/s United States Patent THREE-EGRT WAVEGUIDE SWITCH FOR SELEC- TEVELY CQNNECTENG ONE PQRT T0 EITHER 0F TWQ GTE-1BR PORTS Judd Bless, Bay side, N.Y., and Henry M. Kintzel, Blackensaelr, NJ assignors to Maxson Electronics Corporation, New York, N.Y., a corporation of New York Filed Nov. 17, 1961, Ser. No. 152,995 5 Claims. (Cl. 333-7) This invention relates to microwave switching and particularly to a novel shutter structure which permits signal switching from either of two microwave signal lines to a common line while providing a high degree or" isolation between the desired and undesired transmission paths.

It has been diilicult in the past to make simple precision calibration measurements of the response of a microwave receiver, for example, to the signal from a test source in comparison with that from a particular antenna. Switch devices previously employed for this purpose have been complex, bulky and have not provided suflicient isolation in many instances.

It is therefore the primary object of the present invention to provide a small, simple microwave switch having a novel configuration which achieves a high degree of isolation and prevents undesirable signal leakage into the desired transmission path.

The instant device utilizes a simple waveguide joint or housing and a rotatable cylinder which aligns a pair of ports or openings in the housing with the desired channels in the cylinder to form a transmission path while blocking another path. A third channel in the cylinder is directed into a quarter wavelength high impedance shorted cavity termination in the housing which prevents any distortion in or interference with the desired path, while additional choke cavities positioned around the periphery of the housing eliminate the eifects of leakage from the blocked opening or undesired signal path. The invention will be more fully understood and other objects and advantages will become apparent in the following description and accompanying drawing.

The FIGURE shows a cross-sectional isometric view of the invention.

As shown in the figure, a waveguide junction housing 1 includes a cylindrical hole accommodating a closely fitted cylindrical rotor 2. Two rectangular channels, 3, 4- iorm a path from opposite sides through the center of the cylinder, perpendicular to the axis thereof. A second transverse rectangular path representing the leg of a T- shaped passageway, is formed by another channel 5, in a common plane with the first path.

The housing includes rectangular ports or openings 6 and 7, at each end of the housing, with joints provided for securing waveguides. Opening 6 may be connected to an antenna while opening 7 may connect to a receiver. A third opening 8 located in the housing opposite channel 5 may be connected to another waveguide which leads to a source of test signal. Thus all the openings and channels are located in a common plane.

The housing also includes a rectangular cavity 9 shown positioned in line with channel 5, and having cross-sectional dimensions equal to the waveguides and channels. The cylindrical rotor portion opposite channel 5 has a straight wall section 10 forming a passageway between channels 3 and 4 and is shown in a position blocking access to opening 8. Four additional smaller width rectangular choke cavities 11 are positioned radially about the cylindrical rotor at each corner of the housing. A tuning rod 12 is provided at the antenna input port 6, and a handle 13 may be utilized to manually turn the rotor into the desired switch position. Any suitable driving means such as a motor and gearing may similarly be employed to provide automatic remote operation of the switch. The rotor is preferably made of aluminum having longitudinal cast holes 14 to provide light weight.

In the normal operating position, as shown, signal from the antenna enters at port 6 and travels a straight path through channels 3 and 4 into port 7 leading toward the receiving equipment. The shunting effect of channel 5 is neutralized in a well known manner by cavity 9 which represents a quarter wavelength shorted transmission line stub and thus reflects an apparent high impedance or open circuit to microwave energy at the intersection of channel 5 with path 3, 4. At the same time, any signal which tends to leak around the periphery of the rotor is absorbed by choke cavities 11 and thus interfer ence with the desired main transmission path is minimized. The screws 15 act as stops for the handle 13, so that at each end of its travel, the ports 6 and 7 will line up with the corresponding ports in the housing. Tuning rod 12 may also be adjusted to provide optimum impedance matching and a minimum voltage standing wave ratio, for most efiicient transmission.

When it is desired to provide a test signal to the receiver, the rotor is turned counter-clockwise by 90 degrees so that port 6 is blocked by wall 11), channel 4 is aligned with port 8, channel 5 with port 7 and channel 3 with cavity 9. In this position, cavity 9 again provides a high impedance which prevents shunting of signal by channel 3 and the choke cavities 11 prevent undesired signal leakage around the rotor surface. Microwave energy from the test source is thus caused to turn at a right angle to enter the receiver channel without noticeable loss. The close fit of the rotor and the effect of the choke cavities cause the signal suppression in the undesired path to be well above db. As applied with a typical S-band frequency range of between 2700 to 2900 megacycles, a maximum insertion loss of 0.2 db is realized with a maximum voltage standing wave ratio of 1.4. Although the S-band waveguide dimension measures approximately 2.75 inches in width, the present switch configuration can be mounted on 4" centers.

The present microwave switch thus provides a small, simple shutter device which permits eificient transmission in a selected isolated path while preventing signal leakage from another path.

While only a single embodiment has been illustrated, it is apparent that the invention is not limited to the exact form or use shown, and that many variations may be made in the design and configuration without departing from the scope of the invention as set forth in the appended claims.

What is claimed is:

1. A microwave switch comprising a housing having a pair of aligned waveguide openings positioned at opposite sides of said housing, a third opening positioned at a right angle to said aligned openings, a cylindrical chamher centrally positioned with respect to the longitudinal axis of said housing, a cylindrical rotor fitted closely within said chamber and having a pair of aligned waveguides forming oppositely disposed channels and a third channel positioned at a right angle to said aligned channels, said channels and openings having the same crosssectional dimensions and the walls thereof being coplanar, said rotor having a portion opposite said third channel adapted to block one of said openings, means for rotating said rotor to selectively align two of said channels with two of said openings to form a transmission path for a microwave signal and to block the other opening, means on said housing providing a high impedance to said microwave signal at the other of said channels to prevent interference with said microwave transmission path, and means on said housing to prevent microwave signal leakage around the periphery of said rotor.

2. The device of claim 1 wherein said high impedance means comprises a shorted quarter wavelength cavity aligned with said other channel.

3. The device of claim Z-Wherein-said signal leakage preventing means includes a plurality of choke cavities radially positioned at each corner of said housing.

4. The device of claim 3 wherein one of said aligned openings and said third opening are connected to sources of microwave input signal and said other aligned opening is connected to receiving means, and said rotor channel position selectively connects one of said signal sources to said receiving means.

5. The device of claim 4, including input tuning means in one of said input openings to provide impedance matching and a minimum voltage standing wave ratio in said transmission path.

References Cited in the file of this patent UNITED STATES PATENTS 2,999,213 Olivieri Sept. 5, 1961 FOREIGN PATENTS 718,865 Great Britain Nov. 24, 1954 

1. A MICROWAVE SWITCH COMPRISING A HOUSING HAVING A PAIR OF ALIGNED WAVEGUIDE OPENINGS POSITIONED AT OPPOSITE SIDES OF SAID HOUSING, A THIRD OPENING POSITIONED AT A RIGHT ANGLE TO SAID ALIGNED OPENINGS, A CYLINDRICAL CHAMBER CENTRALLY POSITIONED WITH RESPECT TO THE LONGITUDINAL AXIS OF SAID HOUSING, A CYLINDRICAL ROTOR FITTED CLOSELY WITHIN SAID CHAMBER AND HAVING A PAIR OF ALIGNED WAVEGUIDES FORMING OPPOSITELY DISPOSED CHANNELS AND A THIRD CHANNEL POSITIONED AT A RIGHT ANGLE TO SAID ALIGNED CHANNELS, SAID CHANNELS AND OPENINGS HAVING THE SAME CROSSSECTIONAL DIMENSIONS AND THE WALLS THEREOF BEING COPLANAR, SAID ROTOR HAVING A PORTION OPPOSITE SAID THIRD CHANNEL ADAPTED TO BLOCK ONE OF SAID OPENINGS, MEANS FOR ROTATING SAID ROTOR TO SELECTIVELY ALIGN TWO OF SAID CHANNELS WITH TWO OF SAID OPENINGS TO FORM A TRANSMISSION PATH FOR A MICROWAVE SIGNAL AND TO BLOCK THE OTHER OPENING, MEANS ON SAID HOUSING PROVIDING A HIGH IMPEDANCE TO SAID MICROWAVE SIGNAL AT THE OTHER OF SAID CHANNELS TO PREVENT INTERFERENCE WITH SAID MICROWAVE TRANSMISSION PATH, AND MEANS ON SAID HOUSING TO PREVENT MICROWAVE SIGNAL LEAKAGE AROUND THE PERIPHERY OF SAID ROTOR. 